Ziegler-Natta, Phillips, and Vanadium Catalysts

Phillips catalysts are based on Cr(IV) supported on sUica and alumina. The true structure of the Phillips catalyst is not well understood. A mixture of chromium oxide and silicon oxide (Cr03/Si02) is used to create the active sites. The catalyst does not require addition of chemical activators before the polymerization, since the active site is produced prior to the polymerization by thermal activation at high temperatures (600°C, for instance) [21, 22]. Phillips catalysts are used in both gas-phase and slurry processes. Polyethylene made with Phillips catalysts 

Vanadium catalysts are used to manufacture ethylene-propylene-diene rubbers. 

The catalyst is produced by activating a mixture of VCI3 and VCI4 with AIR3 (alky-laluminum) compounds. Vanadium catalysts are very sensitive to reaction conditions [23]. Changes in the composition of the solvent, polymerization time, and temperature can affect catalyst activity and selectivity. 

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